1. Field of the Invention
The present invention relates to a liquid discharge head including a discharge port for discharging liquid droplets and a liquid chamber communicating to the discharge port, the liquid droplets being discharged by changing the volume of the liquid chamber; and a recording device. The liquid discharge head and the recording device of the present invention are applicable to a recording device for printing on paper, cloth, leather, non-woven cloth, OHP sheet and the like, a patterning device, an application device and the like for applying liquid to a solid object such as a substrate, plate material and the like.
2. Related Background Art
Conventionally, recording devices such as those of the ink jet type are widely used in recording apparatuses such as printers, facsimile machines and the like due to their low noise, low running cost, and easiness to miniaturize and colorize the device. In particular, the application of the liquid discharge head that uses piezoelectric actuator and the like as a patterning device dedicated for device manufacturing is becoming more widespread due to its high degree of freedom of selection of the discharging liquid.
As disclosed in Japanese Patent No. 3379538, the process of discharging the liquid from the discharge port in the liquid discharge head using the piezoelectric actuator will now be described in detail. The volume control for contracting or expanding the volume of the individual liquid chamber is performed by applying displacement that transitions with time to a vibration plate forming one part of an individual liquid chamber by providing an electrical signal. Thus, the liquid extends and starts to project out to the outer side in a liquid column state. Thereafter, the liquid flies over a gap or the recording gap (between liquid discharge head and material to be recorded) while being separated into a plurality of liquid droplets by surface tension.
On one hand, higher resolution in the line of the nozzle (liquid discharge port) and finer amount of discharged liquid amount are being forwarded in applications to the recording device or patterning device. Higher precision of liquid droplet displacement accuracy is also being achieved. A method of narrowing the width of the individual liquid chamber is being studied as a principal method for obtaining higher resolution.
However, when enhancing the resolution by narrowing the width of the individual liquid chamber, in particular, when narrowing the width of the individual liquid chamber in a vendor type liquid discharge head, bending deformation of the vibration plate and further the displacement of the vibration plate resulting therefrom cannot be sufficiently ensured. A desired discharging performance (discharge amount and discharge speed) thus cannot be realized.
Consideration is made in making the thickness of the vibration plate as thin as possible as a countermeasure for such problem. However, the following problems were found from the detailed studies by the inventors.
The object of the studies is the liquid discharge head referred to as a unimorph type (vendor type) piezo-recording head having a piezoelectric body and an electrode formed on the vibration plate. Various types with the thickness of the vibration plate changed were prepared in the piezo-recording head to compare the discharge lifetime. The criteria for determining the lifetime is the period during which liquid leakage is produced at the vibration plate portion due to breakage of the vibration plate. The number of discharging operations up to such point was evaluated. As can be easily assumed, the lifetime due to breakage of the vibration plate was shorter in thinner vibration plates.
In Japanese Patent Application Laid-open No. 2000-272126, an actuator device is disclosed in which the end of the lower electrode is the end of a piezoelectric body active part acting as a substantial drive portion of the piezoelectric element, and a film thickness part is arranged on the insulative layer on the outer side of the end of the lower electrode. As hereinafter described, the position where the portion corresponding to the “film thickness part” is arranged in the example of the present invention is clearly different from that in Japanese Patent Application Laid-open No. 2000-272126.